This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The goal of our experiments is to image pre-neoplastic lesions in patched mutant mice, a model for human medulloblastoma. Our previous studies indicate that 75-85% of these animals have pre-neoplastic cells on the surface of their cerebellum, although only 15% will go on to develop full-blown tumors. We are interested in determining the size, shape and prevalence of these lesions, and in tracking them to determine what happens to them when they do not become tumors. These studies will involve two phases. Phase I: MR histology to determine the characteristics of pre-neoplastic lesions and the sensitivity and resolution with which they can be detected. This will involve high-resolution imaging of 4-6 mice after perfusion. Phase II. Serial in vivo imaging of 4-6 animals to track the disappearance of pre-neoplastic lesions and/or the development of these lesions into tumors. The feasibility of Phase II will be determined during Phase I. Together these studies will provide important insight into the mechanisms of tumor progression in medulloblastoma.